Shortstopping vinyl chloride polymerizations with unsaturated aldehydes



Patented Nev. 4, 1952 2,616,887

UNITED STATES PATENT 'oFFrcE sHoitTs'rot-BING VINYL 'CHEORIDE POLY- ;MERIZATIO'NS. WITH UNSATURATED AL- DEHYDES 'm if 'banzigfNaugatiicig, M 'oiis'; Waterbury, Connr, fas'slgnors to Unit 'd Rubber Gompany, New- York, N. 322, 21

Serial No. 236:075

Itis there fore'desirable to fadd amaterial which aCts-to-terminateor s horts;to fthe vi nyl chlomureeebefiwb f f'Clgin an aqueous ride polymerization rea f-t'er the desired iiiuin una'ere pressuresubstantially equal to partial conversion of p'o meriza blernononier to at'ii 'ted'v to or ,.i. e. out 4 tof9 fib'l'yr il'erhas taken plaearid ve t i jy' ll 'ther fpolyr'ri'erization of "the residual unreacted vinyl rid mbn U 1 iwi a v tiiqi dt a ia efielq esi r efiec'tive short-stoppingagents for vinyl-chloride polymerizations.

In carrying out the present invention; the unsaturated aldehyde is added to the polymerization reactionai'ter partial conversion of polymerizafble' monomer to polymer (usually after about-60% to95'% conversion) andtherearter the unreacted vinyl chloride polymer is removed from the aqueous me ium, and the polyvinyl I chloride recovered in the usual manner. E'x- ,p v amples of unsaturated aldehydes that may be .Rueb'ensaa an v 3 es11 ""ih Chemo-a1 Eh} used are cinnamaldehyde', acrolein. (propenal), ginerifig for December 1950, 'vo1. 57, rages '10'2 methacrolein' (Z-methyl .propenaDl, crotona'ldehyde- 2'-butenal').-:; tiglicgaldehyde '(2-meth'yI-2- 'buten'al'l, oitraljcitronellal, and: mixtures thereof; These unsaturated:aldehydes have ethylenic unsaturation, and the firstjsix have-a", [3 'etnylenic uns'aturation; Smallamounts.ofsuchconnngated di'enes. may satisfactorily be iiseoli to shortstop thexpo'lymeri'zationi reaction, the. amount. efi ectiv'e to shortstop the polymerization generally being less than 2% based on the original vinyl chloride monomer used. For-practical purposes, the amount of: shortstopper may be between 0.1% and. 1% by Weight'oi the original vinyl chloride monomer used. v l

The polymerization reaction is carried out "in the presence or a conventional free radical type polymerization initiator, such as a. peroxygen or am cataly t-r. Examp e 10 erpx en catalysis ar nq aei P, 19 yqr en peroxi e and P e i. a al ali;. r r lm r, alkali p rmia s a k li,.lpe ar nate nand o rox de a d e r Q es e yl e oxide; acetyl benzoyl peroxide, lauroyl peroxide,

tank or in the stripp y l p I crime-demon isfremevea; At "the end or the .ineriz'atiohfit oxide; Examples of; azotiatalysts are alpha, isobutyro'nitrfle; p nietiiex befi;

t apiitiiyl e r. atalytic toe basedon-the vinyl milesirameprep-erties; 'Alsolvihen'the'unre'acted vinyl chloride monomer is removed from the adi'i'e'ousmedium, there maybe some vinyl chlo naemonomer, adsorbe'd'on the polyvinyl chloride 'p'articlesin the aqueous medium, which is not 7 s the e' ctiv has oft'he chiiiiireinoved until drying of the polyvinyl chloride. cals of the pres nt n "as s 'b' ftgtpbi h drsorbrerd l flq mo may poly? agents v'ihyl chloride polymerization vvere hei-1zeenmetOIyvmy1 chloride particles before 55 carried out according to the fdn wmg fb r;

oumen'e: hydroperoxide; tertiary butyl hydroper- Into each of a number of crown capped bottles equipped with self-sealing liners was placed a typical granular polymerization recipe using a water-soluble catalyst (100 parts of liquefied vinyl chloride, 320 parts of water, 0.3 part of potassium persulfate and small amounts of buffering and wetting agents). Polymerizations were carried out at 465 C. Two polymerizations served as controls to show the conversions at an intermediate polymerization (about six hours) and at a final polymerization (about nine and one-half hours) without shortstopping agent. At the end of the intermediate and final polymerization times, monomeric vinyl chloride was immediately vented and percent conversions were obtained. In the test polymerizations, 0.1 part and 0.3 part (based on 100 parts of vinyl chloride monomer used) of cinnamaldehyde were added to separate polymerization bottles at the same time as the intermediate control polymerizations and the heating was continued to the same overall time as the final control polymerization. Vinyl chloride monomer was then vented, and percent conversions were obtained byweighing the polymer.

The percent conversions of monomer to polymer of the control after the intermediate and final polymerization times, and the percent conversions at the final polymerization time where the shortstopper of the present invention was added at the intermediate conversion times, are shown in the following table:

Conversion (Percent) shortstopper added at intermediate conversion Intermediate Final None (intermediate control) 62 A None (final control) 95 0.1 part cinnamaldeliyde 66 0.3 part cinnamaldehyde 65 Conversion (Percent) shortstopper added at intermediate conversion Intermediate Final None (intermediate control) I 55 None (final control) 93 1 part acrolein 56 1 part erotonaldehyde 53 The above work shows that the unsaturated *aldehydes of the present invention are efiective shortstopping agents for vinyl chloride granular polymerizations (the experimental error in the work may be five percent). The chemicals of the present invention are also effective as shprtstoppers for bulk or mass oil-phase vinyl 4 at 60% to conversion of monomer to polymer. In bulk polymerizations, the polymerizations, the polymerization reaction is generally stopped at lower conversions, e. g. around 40%. With the shortstopping agents of the present invention, the polymerization reaction may be stopped at any desired conversion.

In emulsion polymerizations, it is a simple matter to withdraw a sample from the reaction chamber from time to time and to analyze it for total solids in order to determine the percent conversion. On the other hand, it is almost impossible to follow the conversion in a granular polymerization by sampling, because the polymer formed separates so rapidly that a representative sample cannot be obtained. Thus other methods of determining the amount of conversion, and thereby the point at which the reaction should be stopped, must be used in following polyvinyl chloride granular polymerizations. For example, the heat evolved in the reaction mixture can be measured and be directly correlated with the extent of conversion via the known heat of reaction. Also experience has shownthat polyvinyl chloride of good physical characteristics may be obtained by stopping the reaction at the pressure drop which is at the point Where the liquid vinyl chloride monomer disappears (see German Plastics Practice, pages 61 and 77). In systems where the temperature in the reactor is automatically maintained by regulation of the jacket temperature, the pressure drop will be evidenced by a sudden pressure fall. In systems where the pressure in the reactor is automatically maintained by regulation of the jacket temperature, the pressure drop will be evidenced by a rapid rise in jacket water temperature, whereupon the system is thrown out of automatic control and cooling water is introduced into the jacket resulting in the usual fall of pressure in the reactor. Such methods other than sample analyses of determining when to shortstop the reaction at the desired conversion may be used in emulsion polymerization as well as in granular polymerization. The evolution of heat or the viscosity characteristics may be followed in mass polymerization to determine the point at which the shortstopping agent should be added. I

The following illustrates the use of the shortstoppers of the present invention in batch aqueous vinyl chloride polymerization s. A typical emulsion polymerization recipe which uses a water-soluble catalyst parts of liquefied vinyl chloride, 200 parts of water, 0.2 part of potassium persulfate and 1.5 parts of surfaceactive emulsifying agent), or a typical granular polymerization recipe using a water-soluble catalyst (100 parts of liquefied Vinyl chloride, 300 parts of water, 0.3 part of potassium. persulfate, and a small amount of buffering and 'wetting agents), or a typical granular'polymerization recipe using a monomer-soluble catalyst (100 parts of liquefied Vinyl chloride, 300 parts of water, 0.5 part of lauroyl peroxide and a small amount of suspending agent) is agitated in a closed jacketed reaction vessel. The batch is initially heated to the desired reaction temperature between 40 C. and 60 C. and maintained at the desired temperature during the polymerization. The pressure in the reactor at such temperatures will be from 4. to 9 atmospheres until the liquid vinyl chloride is polymerized and the pressure drops. After the pressure starts to drop and before it drops 2 atmospheres,

011 to 1 part cflcinnamaldehyde', iacrolein, methacrolei-n, crotonaldehyde, itiglic aldehyde, citral, or citronellal per 3100 parts of original vinyl chloride used is added so that undesirable further polymerization is prevented. Alternatively, the shortstopping agent may be added at any desired conversion at :thediscretion of the operator. reached and theshortstopadded, the batch may When the desired conversionwhas been be transferred -to the blow-down or storage tank, held there any desired length of time, and then transferred to the stripper when desired for removal of residual :unreacted vinyl chloride monomer. Finishing operations .after residual x-monomer removal are conventional as described in :the literature references referred to above.

The shortstopping. agentsof the present invention :give :a greater uniformity of polymer properties, and :also result in polymers having enhanced heat and light stability.

The sshortstoppers .of' the present invention are applicable to shortstopping otmodified. vinyl chloride polymers which are made by copolyalkyl .acrylate, e. gsmethyl acrylate, or an alkyl :alkacrylate, e. g. methyl 'methacrylate, or an 9 .alkyl maleate, e. g; dim'ethyl maleate, diethyl male'ate, 'isobutyl maleate, and mixtures thereof. Such polymerizations are similarto the homopolymerization of polyvinyl chloride but with asomewhat broader ran e of reaction temperatures from 25 C. to 100 0., depending on the particular vinyl chloride copolymer being made (see German Plastics Practice, pages 76-78). The same amount of shortstopping agent based on the amount of 'vinyl chloride employed may be added after partial conversion, generally at about 60% to 95% conversion of polymerizable monomeric material to polymeric material.

In view of the many changes and modifications that may be made without departing from the principles underlyingthe invention, reference should be made to the appended claims for an understanding of the scope of the protection afforded the invention.

Having thus described our invention, what we claim and desire to protect by Letters Patent is:

1. In the process of preparing a vinyl chloride polymer by the polymerization of material of the group consisting of vinyl chloride and mixtures of vinyl chloride with up to 20% by weight of the vinyl chloride of other monoolefinic material which is copolymerizable with vinyl chloride, the step comprising adding a small amount of unsaturated aldehyde having ethylenic unsaturation to the reaction mixture during polymerization to stop the same after partial conversion of polymerizable monomeric material to polymeric material.

2. In the process of preparing a vinyl chloride polymer by the polymerization of material of the group consisting of vinyl chloride and mixtures of vinyl chloride with up to 20% by weight of the vinyl chloride of other monoolefinic material which is copolymerizable with vinyl chloride, the step comprising adding a small amount of unsaturated aldehyde having 41, 3 ethylenic' unsaturation to the reaction mixture during polymerization to stop the same after partial conversion of polymerizable monomeric material to polymeric material,

1 (:3. i In the process- :of rpreparingra vinyl chloride polymer byzthe polymerizationzof:materialoi the group consisting :of vinyl, chloriderand mixtures of vinyl chloride with up :to 120% by weight of the vinyl chloride of other monoolefinicimaterial which is copolymerizable with vinyl chloride, the step comprising adding "a :small amount of cinnamaldehyde to the reaction mixture during :polymerization to stop the :same after partial conversion of polymerizable monomeric 'mamrial to polymeric material. I v

.4. In the process of preparing a'vinyl chloride polymer by the polymerization :of material of the group consisting 'of vinylxchloride :and mixtures of vinyl chloride'twith upto 20% by'weight of. the vinyl. chloride of "othermonoolefinic material which .is copolymerizable. with vinyl chloride, the step comprising adding "a .sm'allamount of acrolein .to' the reaction mixture-during polymerization to 'stop'the 'sam'eaafter partial conversion of polym'erizable zmonomerichmaterial to polymeric material.

'5. In the process. of preparing aivinyl chloride polymer .by the polymerizationof material (of :the group consisting .of vinyl chloride and mixtures of vinyl chloride with up ito120% by weight of the vinyl chloride of other monoolefinicimaterial which is copolymerizable with vinyl chloride,

the step comprising adding :a small amountoi crotonaldehyde to the reaction mixture :during polymerization to "stop the same .after partial conversion of polymerizable monomeric material to polymeric material.

6. In'the process of preparing polyvinyl chloride by the polymerization :of vinyl chloride in an aqueous medium, the step comprising adding 0.1% to 1% of unsaturated aldehyde having ethylenic unsaturation based on the weight of the original monomeric vinyl chloride used to the reaction mixture during polymerization to stop the same after about 60% to conversion of vinyl chloride .monomerto polyvinyl chloride.

'7. The method of preparing a vinyl chloride polymer which comprises subjecting material of the group consisting. of vinyl chloride and mixtures of vinyl chloride with up to 20% by weight of the vinyl chloride of other monoolefinic material Which is copolymerizable with vinyl chloride to polymerizing conditions in an aqueous medium in the presence of a polymerization catalyst, and after about 60% to 95% conversion of polymerizable monomeric material to polymeric material adding to the polymerization reaction 0.1% to 1% based on the weight of the original monomeric vinyl chloride used of unsaturated aldehyde having ethylenic unsaturation to stop polymerization of unreacted polymerizable monomeric material, and thereafter removing unreacted polymerizable monomeric material from the aqueous medium.

8. The method of preparin a vinyl chloride polymer which comprises subjecting material of the group consisting of vinyl chloride and mixtures of vinyl chloride with up to 20% by weight of the vinyl chloride of other monoolefinic material which is copolymerizable with vinyl chloride to polymerizing conditions in an aqueous medium in the presence of a polymerization catalyst, and after about 60% to 95% conversion of polymerizable monomeric material to polymeric material adding to the polymerization reaction 0.1% to 1% based on the weight of the original monomeric vinyl chloride used of unsaturated aldehyde having a, p ethylenic unsatu- 7 ration to stop polymerization of unreacted polymerizable monomeric material, and thereafter removing unreacted polymerizable monomeric material from the aqueous medium.

9. The method of preparing polyvinyl chloride which comprises subjecting vinyl chloride to polymerizing conditions in an aqueous medium in the presence of a peroxygen catalyst, and after partial conversion of vinyl chloride monomer to polyvinyl chloride adding to the polymerization reaction a small amount of unsaturated aldehyde haVing ethylenic unsaturation to stop polymerization of unreacted vinyl chloride monomer, and thereafter removing unreacted vinyl chloride from the aqueous medium.

10. The method of preparing polyvinyl chloride which comprises subjecting vinyl chloride to polymerizing conditions in a closed vessel in the presence of a peroxygen catalyst in an aqueous medium at a temperature between 40 C. and 60 C. under a pressure substantially equal to saturated vapor pressure of about 4 to 9 atmospheres,.and after the pressure begins to drop and before it has dropped 2 atmospheres adding to the polymerization reaction a small amount of unsaturated aldehyde having ethylenic unsaturation to stop polymerization of unreacted vinyl chloride monomer, and thereafter removing unreacted vinyl chloride from the aqueous medium.

11. The method of preparing polyvinyl chloride which comprises subjecting vinyl chloride to polymerizing conditions in a closed vessel in the presence of a peroxygen catalyst. in an aqueous medium at a temperature between 40 C. and 60 C. under a pressure substantially equal to its saturated vapor pressure of about 4 to 9 atmospheres, and after the pressure begins to drop and before it has dropped 2 atmospheres adding to the polymerization reaction a small amount of unsaturated aldehyde having a, B ethylenic unsaturation to stop polymerization of unreacted vinyl chloride monomer, and thereafter removing unreacted vinyl chloride from the aqueous medium.

12. The method of preparing polyvinyl chloride which comprises subjecting vinyl chloride to polymerizing conditions in a closed vessel in the presence of a peroxygen catalyst in an aqueous medium at a temperature between 40 C. and C. under a pressure substantially equal to its saturated vapor pressure of about 4 to 9 atmospheres, and after the pressure begins to drop and before it has dropped 2 atmospheres adding to the polymerization reaction a small amount of cinnamaldehyde to stop polymerization of unreacted vinyl chloride monomer, and thereafter removing unreacted vinyl chloride from the aqueous medium.

13. The method of preparing polyvinyl chloride which comprises subjecting vinyl chloride to polymerizing conditions in a closed vessel in the presence of a peroxygen catalyst in an aqueous medium at a temperature between 40 C. and 60 C. under a pressure substantially equal to its saturated vapor pressure of about 4 to 9 atmospheres, and after the pressure begins to drop and before it has dropped 2 atmospheres adding to the polymerization reaction a small amount of acrolein to stop polymerization of unreacted vinyl chloride monomer, and thereafter removing unreacted vinyl chloride from the aqueous medium.

14. The method of preparing polyvinyl chloride which comprises subjecting vinyl chloride to polymerizing conditions in a closed vessel in the presence of a' peroxygen catalyst in an aqueous medium at a temperature between 40 C. and 60 C. under a pressure substantially equal to its saturated vapor pressure of about 4 to 9 atmospheres, and after the pressure begins to drop and before it has dropped 2 atmospheres adding to the polymerization reaction a small amount of crotonaldehyde to stop polymerization of unreacted vinyl chloride monomer, and thereafter removing unreacted vinyl chloride from the aqueous medium.

NIEYER H. DANZIG. LEONARD F. MAROUS.

No references cited. 

1. IN THE PROCESS OF PREPARING A VINYL CHLORIDE POLYMER BY THE POLYMERIZATION OF MATERIAL OF THE GROUP CONSISTING OF VINYL CHLORIDE AND MIXTURES OF VINYL CHLORIDE WITH UP TO 20% BY WEIGHT OF THE VINYL CHLORIDE OF OTHER MONOOLEFINIC MATERIAL WHICH IS COPOLYMERIZABLE WITH VINYL CHLORIDE, THE STEP COMPRISING ADDING A SMALL AMOUNT OF UNSATURATED ALDEHYDE HAVING ETHYLENIC UNSATURATION TO THE REACTION MIXTURE DURING POLYMERIZATION TO STOP THE SAME AFTER PARTIAL CONVERSION OF POLYMERIZABLE MONOMERIC MATERIAL TO POLYMERIC MATERIAL. 